Heteropentadienyl Analogues of Half-Open Ruthenocenes: Metal-Ligand Interactions and Electronic Structure Perturbations
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- 作者：Asha Rajapakshe ; M. Angeles Paz-Sandoval ; J. Alfredo Gutierrez ; M. Elena Navarro-Clemente ; Patricia Juá ; rez Saavedra ; Nadine E. Gruhn ; and Dennis L. Lichtenberger
- 刊名：Organometallics
- 出版年：2006
- 出版时间：April 10, 2006
- 年：2006
- 卷：25
- 期：8
- 页码：1914 - 1923
- 全文大小：430K
- 年卷期：v.25,no.8(April 10, 2006)
- ISSN：1520-6041
文摘
The electronic structures of molecules of the form Cp*Ru(
mages/gifchars/eta.gif" BORDER=0 >5-Pdl) (where Cp* = mages/gifchars/eta.gif" BORDER=0 >5-pentamethylcyclopentadienyl and Pdl = 2,4-dimethylpentadienyl and various heteropentadienyl ligands, including theazapentadienyl ligand 1-tert-butyl-3,5-dimethyl-1-azapentadienyl and the oxopentadienyl ligands 2,4-dimethyl-1-oxopentadienyl and 2,4-di-tert-butyl-1-oxopentadienyl) have been investigated using photoelectron spectroscopy and computational methods. The photoelectron spectra of these half-openmetallocenes allow direct insight into the bonding capabilities of pentadienyl ligands and the influencesof heteroatom substitution on the electronic structure. The number of separate valence ionization bandsthat are observed corresponds directly to the number of occupied valence metal d orbitals and highestoccupied mages/gifchars/pi.gif" BORDER=0 > orbitals of the Cp* and Pdl ligands plus (in the case of the heteropentadienyl ligands) anionization that derives from the heteroatom (oxygen or nitrogen) lone pair orbital that is in the plane ofthe ligand. The heteropentadienyl ligand substitution has strong effects on both the ligand- and the metal-based ionizations. Interestingly, the ease of oxidation of the molecules does not follow the expectedperiodic trend of increasing ionization energy with increasing electronegativity of heteroatom substitution.Density functional calculations give orbital energies and characters for the Cp*Ru(Pdl) molecules ingood agreement with those determined by experiment and offer an explanation of the unusual trend inionization energies with heteroatom substitution. The calculations also show enhanced Ru-cyclopentadienyl bonding accompanying a weakening of Ru-pentadienyl bonding as the pentadienyl ligand becomesmore electronegative with heteroatom substitution, which is important for understanding the relativestructures and chemical reactivities of heteropentadienyl-metal complexes.